This invention relates generally to an improved electro-optical display and particularly to an improved electro-optical display for use in solid state electronic timepieces. As the popularity of solid state electronic timepieces such as wrist watches has increased, so has the popularity of digital displays. Such digital displays have been comprised of light emitting diodes or liquid crystal cells.
Because the size of a battery which can be included in a wrist watch is extremely small, the use of such batteries to supply the energy required to light up displays formed from light emitting diodes has been less than completely satisfactory. Because light emitting diodes require a considerable amount of power it has been the practice to provide a manual switch which lights up the light emitting diode display only at the time that the wearer of the wrist watch desires to known the time.
Similarly, although liquid crystal display cells require considerably less power than light emitting diodes such liquid crystal display cells can on the average be maintained for perhaps a little more than a year in a constantly lightened state. High precision electronic wrist watches having quartz crystal oscillators as a time standard have gained recognition because of the long period of time over which they remain accurate without the necessity of making adjustments thereto. The time period over which liquid crystal display elements remain reliable in comparison to that of such electronic wrist watches is considerably shorter. Because the liquid crystal cells have a significantly shorter operating life than the quartz crystal oscillator the effective life of the timepiece is limited by the life of the display cells, thus decreasing the effective market value of such digital display wrist watches.
Finally, a further attempt to provide long lasting optical display elements has been the use of single crystals such as a GMO. A single crystal requires sophisticated manufacturing techniques and must be processed giving consideration to the crystal axis as an optical element. Accordingly, the cost of producing such single crystal elements is high, as is the cost of such materials required in the manufacturing process. Moreover, because optional elements cannot be added to the single crystal, the improvement of the physical characteristics thereof is rendered difficult.